1. Field of Invention
The invention relates to a method of making an ID circuit and, in particular, to a method for making an ID circuit of the inkjet chip in an inkjet printer.
2. Related Art
Since the inkjet print head cartridges for accommodating different inkjet chips may have similar shapes, the printer has to be able to self-test whether the inserted print head is correct to prevent the user from putting the print head into an incorrect carriage. This is the theme of the invention. In particular, for the inkjet chips of a shared chip module, the cartridge, nozzle plate, and TAB for monochromic (black) and multi-color (color) inkjet chips are able to use shared elements so as to keep the cost low while at the same time maintain the quality easily during the later assembly and packaging processes. One drawback, however, is that the print head using a shared inkjet chip is likely to confuse the user so that it is put into an incorrect carriage. Therefore, there is a higher demand for an ID circuit for inkjet chips.
There were several designs of inkjet chip ID available in the prior art. In the U.S. Pat. No. 4,872,027, it was proposed to insert different resistors among different circuit pads of the inkjet chip. If some pads form a loop with low resistance, it then identifies itself as a particular type of inkjet chip. Likewise, if some other pads form a loop, then it is another type of chip.
After active inkjet chips with driving circuits appear, the inkjet chip ID circuit design becomes even more complicated. Nevertheless, the advantage is that no additional circuit connecting points are required. In the U.S. Pat. No. 5,363,134, the ID circuit made use of the address pads originally for controlling the actions of particular nozzles. When some address pad was supplied with a high voltage, the loop resistance passing through the transistor was detected. The loop contained a fuse to define the type of the inkjet chip. If the fuse was kept, then the loop had low resistance; if the fuse was burned, then the loop was open.
In the U.S. Pat. No. 5,831,649, ROM was employed to constitute an N-bit code. In the U.S. Pat. No. 5,757,394, the ID circuit is comprised of a series of transistors. Address lines were used to set ON and OFF of the transistors to read out the code in order. The coding was determined by whether each drain is connected to the gate of the next transistor in the circuit.
In the U.S. Pat. No. 5,940,095, the inkjet chip ID circuit consisted of a series of one-bit shift registers. Each shift register was pre-coded by connecting its source to a high voltage or the ground. To read out the code in order, a parallel load and two clocks were provided.
In addition to chip circuit designs, the U.S. Pat. No. 6,161,915 proposed the design of accompanying the chip circuit with a TAB. When a signal was provided, certain TAB pads would generate a corresponding voltage. Different inkjet chips may be given with the same ID circuit, but the coding of different inkjet chips is determined by covering or uncovering some particular TAB pads.
It is an objective of the invention to associate different types of inkjet chips with different ID""s so that an inkjet printer may easily identify the inkjet chip.
It is another objective of the invention to prepare monochromic and color inkjet chips with a shared chip module through the position arrangement of the ID circuit and the ink feed slot during the formation process of the ink feed slot. This simplifies the manufacturing process of the inkjet chip by having no additional requirements.
The disclosed method does not only apply to the manufacturing of the ID circuit for normal inkjet chips, it is also applicable to the preparation of inkjet chips for a shared chip module. The cartridge, nozzle plate and TAB for monochromic and color inkjet chips can thus be shared. In this case, if the ID circuits of different types of inkjet chips were made by photolithographic process using masks with different patterns, the advantage of a shared chip is sacrificed. Consequently, we install the inkjet chip ID circuit of the shared chip module near the ink feed slot. Subsequent ink feed slot processing makes different ink feed slots for different monochromic and color inkjet chips. At the same time, the inkjet chip ID circuit is disconnected in a particular type of inkjet chip, forming an open-loop ID circuit, whereas it is kept as a closed-loop ID circuit in another type of inkjet chip. Through this kind of circuit structure, it is then possible to identify different types of inkjet chips immediately.
According to the disclosed method, the ID circuit of inkjet chips can adopt the circuits mentioned above. For example, it may be an ID circuit using different resistances, or an ID circuit with transistors. However, the invention further provides a distinct manufacturing method. Based upon the design that monochromic and color inkjet chips of a shared chip module use the same cartridge and TAB, the manufacturing process and structure of existing inkjet chips of a shared chip module are not modified too much. The only difference is that a new method is proposed after the above step for making the ink feed slot and the ID circuit. According to the invention, some circuit of the ID circuit is purposely installed near the ink feed slot of the inkjet chip. Utilizing the size or position of the ink feed slot, the ID circuit is an open or closed loop during the manufacturing process of the ink feed slot, thereby forming an ID circuit that can identify the types of inkjet chips.